Satellite Angular Velocity Estimation Using Star Tracker Interpolation
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Solution Overview
Problem
Current methods for estimating the angular velocity of satellites rely on costly and complex gyroscopic sensors, while star trackers are primarily used for attitude estimation, with limited practical use for measuring angular velocity around the satellite's center of mass, and existing solutions for using star trackers to estimate angular velocity are limited to low motion values and require increased measurement frequency.
Innovation Solution
A method that uses one or more star trackers to estimate angular velocity by acquiring and processing images to identify star clusters, compute star versors, and apply polynomial interpolation to estimate angular velocity, independent of the sensor's operating frequency, allowing for accurate estimation of both angular velocity and attitude without the need for gyroscopes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If gyroscopic sensors are used to estimate angular velocity, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent replaces mechanical gyroscopic sensors with an optical-based computational system. Instead of using physical gyroscopes to measure angular velocity, the system uses star tracker optical measurements combined with polynomial interpolation algorithms to estimate angular velocity, thereby eliminating complex mechanical components while maintaining measurement capability
Solution Approach 2:
The patent creates a computational model that replicates the angular velocity measurement function. By using polynomial interpolation to model the relationship between star position changes and angular velocity, the system creates a virtual measurement system that substitutes for physical gyroscopes, reducing hardware complexity
2Device complexity
If star trackers are used for angular velocity estimation, then cost is reduced, but measurement precision deteriorates for high angular velocities
Solution Approach 1:
The patent introduces dynamic adaptation by selecting different polynomial orders based on the measured angular velocity magnitude. For low angular velocities, lower-order polynomials are used, while for high angular velocities, higher-order polynomials are selected to maintain accuracy. This dynamic adjustment allows the system to adapt to varying operational conditions and maintain precision across the full range of motion
Solution Approach 2:
The patent changes the mathematical model parameters (polynomial order) based on the operating conditions. By adjusting the polynomial order parameter according to the angular velocity range, the system optimizes measurement accuracy for different motion regimes, transforming a static measurement system into one that can accurately handle both low and high angular velocities
3Measurement precision
If star tracker measurement frequency is increased to improve angular velocity estimation, then measurement precision is improved, but productivity decreases
Solution Approach 1:
The patent applies partial action by using polynomial interpolation of varying orders rather than always using the maximum measurement frequency or highest-order polynomial. This allows the system to achieve sufficient measurement precision with moderate computational effort, avoiding the need for excessive measurement frequency increases while maintaining adequate accuracy for the application
Data Source
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AI summary
The invention concerns a method (1) for estimating the angular velocity (and, preferably, also the attitude) of a space platform (for example, a satellite, a space vehicle, or a space station) using only the information provided by one or more optical sensors, such as one or more star trackers (71, 72, 73), one or more colour and/or black and white cameras or video cameras, one of more infrared sensors, etc.